PCB Glossary


Printed Circuit Board Terminology

The PCB glossary is implemented to provide you definitions to some of the words and abbreviations you will come across in doing business with PCB Basket. It gives useful information about PCB circuits, circuit board design, and circuit board construction.

A

Analog Circuit

An electrical circuit that provides a continuous quantitative output as a response from its input.

Annular Ring

that portion of conductive material surrounding a hole.

Aperture

A description of the shape and size of the tool used to create a pad or track. The term comes from the days of vector photo plotters, where film was exposed by shining light through apertures (shaped holes) arrayed around the edge of a disk (or "aperture wheel"). Each aperture corresponded to a different D code in the Gerber data. Today, photoplotters use lasers to expose the film but the term "aperture" persists.

Array

A group of elements or circuits (or circuit boards) arranged in rows and columns on a base material.

Artwork

Artwork for printed circuit design is photoplotted film (or merely the Gerber files used to drive the photoplotter), NC Drill file and documentation which are all used by a board house to manufacture a bare printed circuit board.

Assembly

1. The process of positioning and soldering components to a PCB.

2. Act or process of fitting together parts to make a whole.

Assembly File

A drawing describing the locations of components on a PCB.

ATE

Automated Test Equipment. Equipment that automatically tests and analyzes functional parameters to evaluate performance of the tested electronic devices.

B

BGA

Short for ball grid array, this is a type of component packaging used in integrated circuits (ICs) for surface mounting. They can ensure high-speed efficiency since they use columns of balls instead of pins. BGAs are usually used to mount devices like microprocessors on PCBs permanently.Bare Board - An unpopulated PCB.

Board

printed circuit board. Also, a CAD file which represents the layout of a printed circuit.

Body

The portion of an electronic component exclusive of its pins or leads.

BOM

Bill of Materials. A list of components to be included on an assembly such as a printed circuit board. For a PCB the BOM must include reference designators for the components used and descriptions which uniquely identify each component.

Bottom Layer

That bottom side of the printed circuit board.

Built-In Self Test

An electrical testing method that allows the tested devices to test itself with specific added-on hardware.

Burried Via

A via hole that does not extend to the surface of a printed board.

Burr

A ridge left on the outside copper surface after drilling.

C

CAD

Computer Aided Design. A system where engineers create a design and see the proposed product in front of them on a graphics screen or in the form of a computer printout or plot. In electronics, the result would be a printed circuit layout.

CAM Files

CAM means Computer Aided Manufacturing. These are the data files used directly in the manufacture of printed wiring. The types of CAM files are 1) Gerber file, which controls a photoplotter, 2) NC Drill file, which controls an NC Drill machine and 3) fab and assembly drawings in soft form (pen-plotter files). CAM files represent the valuable final product of PCB design. They are handed off to the board house which further refines and manipulates CAM data in their processes, for example in step-and-repeat panelization. Some PCB design software companies refer to all plotter or printer files as CAM file, although some of the plots may be check plots which are not used in manufacture.

Capacitance

The property of a system of conductors and dielectrics which permits storage of electricity when potential difference exists between conductors.

Card

Another name for a printed circuit board.

Circuit Design

The creation of the functional description and diagram (the schematic) of an electronic circuit.

Clearance

1)clearance means space between different networks. Usually if you want design a low-cost PCB setup the clearance 7mil-10mil, and we suggest>=10mil.

2) The shortest path between two conductive parts, or between a conductive part and the bounding surface of the equipment, measured through air.

Coating

A thin layer of material, conductive, magnetic or dielectric, deposited on a substance surface.

Component

Any of the basic parts used in building electronic equipment, such as a resistor, capacitor, DIP or connector, etc.

Connectivity

The intelligence inherent in PCB CAD software which maintains the correct connections between pins of components as defined by the schematic.

Connector

A plug or receptacle which can be easily joined to or separated from its mate. Multiple-contact connectors join two or more conductors with others in one mechanical assembly.

Controlled Impedance

The matching of substrate material properties with trace dimensions and locations to create specific electric impedance as seen by a signal on the trace.

Creepage

The shortest path between two conductive parts, or between a conductive part and the bounding surface of the equipment, measured along the surface of the insulation.

D

DFA

Design for Assembly.

DFF

Design for Fabrication.

DFM

Design for Manufacturing.

DFR

Design for Reliability.

DFT

Design for Test.

Differential Signaling

A method of signal transmission through two wires which always have opposite states. The signal data is the polarity difference between the wires: Whenever either is high, the other is low. Neither wire is grounded.

Die

Integrated circuit chip as diced or cut from a finished wafer.

Dielectric

An insulating medium which occupies the region between two conductors.

Digital Circuit

A circuit which operates like a switch (it is either "on" or "off"), and can make logical decisions. It is used in computers or similar decision-making equipment.

DIP

Dual In-line Package. A type of housing for integrated circuits. The standard form is a molded plastic container of varying lengths and 0.3 inch wide (although there are other standard widths), with two rows of through-hole pins spaced 0.1 inch between centers of adjacent pins.

Double-Sided Assembly

PCB assembly with components on both sides of the substrate.

Double-Sided Board

A printed board with a conductive pattern on both sides.

DRC

Design Rule Check. Carried out to make sure the data given to manufacture a PCB follows good practise before the artworks are made to produce the printed circuit board.

DS

Double-sided PCB, has 2 conductive layers (Top and Bottom).

E

Edge Clearance

The smallest distance a component or track is from the edge of a PCB.

Epoxy

A family of thermosetting resins used in the packaging of semiconductor devices. Epoxies form a chemical bond to many metal surfaces.

Etching

Removing unwanted metallic substance by chemical or chemical/electrolytic process.

EMC

An acronym for electromagnetic compatibility, EMC refers to the capability of a piece of equipment or system to run without producing excessive electromagnetic interference. Too much electromagnetic interference can interfere with or damage other pieces of equipment within the same electromagnetic environment.

ENIG

Electroless Nickel Immersion Gold, metallic solderable surface finish for component contact areas and for mechanical contacts like keypad or spring loaded contact.

Excellon

NC Drill file format. An ASCII format used in a file which drives an NC Drill machine. The earliest NC Drill machines were made by Excellon Automation Company. The format is in broad use, although the company has been sold.

F

Fabrication Drawing

A drawing used to aid the construction of a printed board. It shows all of the locations of the holes to be drilled, their sizes and tolerances, dimensions of the board edges, and notes on the materials and methods to be used. Called "fab drawing" for short. It relates the board edge to at least on hole location as a reference point so that the NC Drill file can be properly lined up.

FC

Flexible Circuit, flexible circuitry, flexcircuit or flex circuit.

Flash

1. v. To turn a vector photoplotter lamp on for a brief but precise duration and then off, during which time the relative positions of the lamp and film remain fixed. This exposes the film with the image of a small object (the size and shape of which is controlled by the transparent portion of an aperture ).

2. n. A small image on film created in such wise or as directed by a command in a Gerber file .) The maximum size (x or y dimension) for a flash varies from one photoplotting shop to another, but is commonly ½ inch.

Flex Circuit

Flexible circuit, or flexcircuit; a printed circuit made of thin, flexible material.

Footprint

Land pattern. The arrangement of pads (in surface-mount technology) or through-holes (in through-hole technology) used to physically attach and electrically connect a component to a printed circuit board.

Fiducal

Fiducial marks are dots etched on board panel usually required by SMD assembly (provide viewing targets for camera to locate correct position).

Finger

A gold-plated terminal of a card-edge connector. Also see Gold Finger.

Flux

The material used to remove oxides from metal surfaces and enable wetting of the metal with solder.

FR-1

A low-grade version of FR-2.

FR-2

A NEMA grade of Flame-Retardant industrial laminate having a substrate of paper and a resin binder of phenolic. It is suitable for printed circuit board laminate and cheaper than the woven glass fabrics such as FR-4.

FR-4

The most commonly used PCB board material. "FR" stands for Flame Retardant and "4" means woven glass reinforced epoxy resin.

FR-6

Fire-Retardant glass-and-polyester substrate material for electronic circuits. Inexpensive; popular for automobile electronics.

Functional Test

The electrical testing of an assembled electronic device with simulated function generated by the test hardware and software.

G

Gerber

This format is an open 2D binary vector image file format. It is the standard file used by printed circuit board (PCB) industry software to describe the printed circuit board images: copper layers, solder mask, legend, etc.

Gold Fingers

These are connectors found on the edge of a PCB after the board has been plated with gold. Hard, smooth and flat, these fingers are excellent conductors, supporting edge-to-edge connections.

Ground Layer

A conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding or heat sinking.

Grid

Another term for an electrical grid, an interconnected electrical network that transmits power.

H

HASL

Hot Air Solder Levelling.

HDI

High Density Interconnect.

I

IC

Integrated Circuit.1) miniaturized electronic circuit that has been manufactured as a chip (die).2) A packaged chip.

Impedance Control

Controlling impedance in PCB manufacturing, Impedance is an electrical property of a transmission line in PCB, for example 50ohm +/-10%.

IPC

The Institute for Interconnecting and Packaging Electronic Circuits, the final American authority on how to design and manufacture printed wiring. In 1999, IPC changed its name from Institute of Interconnecting and Packaging Electronic Circuits to IPC. The new name is accompanied with an identity statement, Association Connecting Electronics Industries. The group helps enterprises achieve greater business success by helping them meet rigorous manufacturing standards, which, in turn, improve overall quality standards.

J

Jumper

Jumper wire forms electrical connections between two points on printed circuit board. Sometimes it happens while designing PCB that tracks may overlap each other as we make connections.

L

Layer

Layer of the Printed Circuit Board. PCB is defined as a number of copper layers in a well-defined sequence. Copper layers are usually just named layers or also called SIGNAL layer. 1-layer PCB = single sided PCB.

Lead

A terminal on a component.

Legend

The print on a PCB showing the location of components and orientation. Can also be used to display a logo or part number of the printed circuit board.

LPI

Stands for Liquid PhotoImageable. Refers to liquid photoimageable solder mask.

M

Manhattan Length

The length of the two sides of a right triangle as a distance between two points, as opposed to the hypotenuse. (Derived from the Manhattan algorithm for determining the length of a taxicab trip following streets and avenues on the island of Manhattan, NY.) Routing of traces in orthogonal patterns in a PCB design, or in a semiconductor chip, follows the same pattern as streets and avenues in a city. The minimum distance between two component leads, or two nodes on a chip, when routing on 90 degrees is the Manhattan length.

Master Aperture List

1. An aperture list which is used for every PCB designed by a PCB design service bureau or department. If a new design requires one or more new apertures, they are added to the list, either at the end or in some previously unused positions set aside for that purpose. The previously used aperture positions are never edited to change their parameters. Thus, the updated list can still be used as a master for any previous PCB's designed. This type of master aperture list became possible only with the advent of laser photoplotters , which can have upwards of 1000 positions if need be.

2. Any aperture list which is used with two or more PCB's would be called the master aperture list for that set of PCBs.

MIL

A "mil" is another way to say a thousandth of an inch. It's also the equivalent of a "thou".

Mid-Layer

The internal layer of the printed circuit board.

mm

"mm" is another way to express a millimeter or a thousandth of a meter.

Motherboard

This is the main board in a computer or electric device. The motherboard carries key interconnections and components that support the primary functions of the device.

Mounting Hole

This hole is intended to secure the PCB to its final location in a device. To ensure there is no interference, all mounting holes are non-conductive and unplated.

Multy-layer PCB

This is a type of PCB with at least three conductive layers of trace and components.

N

NC Drill

This is a more common name for a Numeric Control drill machine. This type of machine is what assemblers use to drill holes in PCBs.

Node

This is a pin or lead that is connected to at least one wire.

NPTH

Non-Plated Through Hole.

O

OSP

Organic Solderability Preservatives.

Outer Layer

The top and bottom sides of any type of circuit board.

Oz

Ounce, is fairly commonly used to define nominal copper thickness in non-plated PCB layers, for example 1 oz = 35u; 1/2 oz = 18u.

P

Package

Decal or printed wiring board component. A type of PCB component which contains a chip and acts to make a convenient mechanism for protecting the chip while on the shelf and after attachment to a PCB. With its leads soldered to a printed circuit board, a package serves as the electrical conduction interface between the chip and the board. An example is a DIP.

Pad

The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components.

Panel

Material (most commonly an glass/epoxy-copper laminate known as core) sized for fabrication of printed circuit boards. Panels come in many, many sizes, the most common being 12" by 18" and 18" by 24". Subtract 1/2" to 1" margins (check with your board house) from the panel size to arrive at the space available for printed circuitry.

Paste Mask

A stainless steel template in a tightened frame, with holes corresponding to land patterns on the bare board that are either cut, punched, or drilled with a laser. The solder stencil is used at the beginning of the circuit assembly process where it is placed on top of a bare board, solder paste is pushed through the holes, then the stencil is lifted away. This leaves small solder paste deposits on the bare board, onto which components are placed.

PCB

A printed circuit board, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate.

Pick and Place

A manufacturing process when assembling surface mount components to a PCB. The component is selected and placed onto a specific location on to the printed circuit board by means of a dedicated machine.

Polygon

It refers to an area on a printed circuit board filled with copper (the metal used to make connections in printed circuit boards). Copper pour is commonly used to create a ground or power plane. Another reason for using copper pour is to reduce the amount of etching fluid used during manufacturing.

Power Layer

Power planes are solid copper layers shorted to a fixed potential. And power planes are connected to one of your onboard voltages. Normally, these can be located within the internals of your board.

PREPREG

Also called PP, is the key material for multi-layer PCB manufacturing. it is primarily composed of resin and strengthening material that is then classified into glass-fiber cloth, paper base, compound material etc.

Punching

Using dies to punch component holes, usually in single & double-sided PWBs.

PWB

When a PCB has no components installed, it is less ambiguously called a printed wiring board (PWB) or etched wiring board, as the term printed circuit board tends to imply a complete manufactured circuit on a board.

Q

QC

Quality Control.

R

RoHS

Restriction of Hazardous Substances, is one of a handful of European legislation intended to eliminate or severely curtail the use of cadmium, hexavalent chromium, and lead in all products from automobiles to consumer electronics.

S

Schematic

A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement.

Signal

Land pattern. The arrangement of pads (in surface-mount technology) or through-holes (in through-hole technology) used to physically attach and electrically connect a component to a printed circuit board.

Signal Layer

Circuits designed to carry certain speed signals throughout a circuit board and its components.

Silk Screen

Silk Screen is a print on PCB that provide information about components or connection on PCB in text or picture format.

Single Side PCB

The pads and traces are on the one side of the board only.

Slot

A slot in a printed circuit board that polarizes it, thereby permitting it to be plugged into its mating receptacle with pins properly aligned, but preventing it from being reversed or plugged into any other receptacle.

Slot Hole

Non-round holes on a PCB that may or may not be plated. These are often required for specific components.

SMD

Surface Mount Device. It refers to components designed to be soldered on the surface of PCBs, rather than through a thru-hole.

SMT

Surface Mount Technology.

Solder Bumps

Solder balls.

Solder Mask

This is an isolating mask that covers the copper of the circuit Board to protect the circuit against electrical shorts and unwanted connection in case of a contact with any conductive material.

Stackup

Printed circuit board (PCB) stackup describes the basic construction of a PCB. Specifically, the stackup defines the total number of PCB layers and the type of each of these layers. While the order of some layers is obvious from their names, such as Top Overlay, Bottom Solder Mask, etc., the location of other layers is not so obvious, e.g., Internal Ground Plane 1 or Internal Routing Layer 3. Without a clear description of the PCB stackup, the specific location of these internal layers is undefined.

Symbol

A simplified design representing a part in a schematic circuit diagram.

T

Tenting

A printed circuit board fabrication method of capping plated-through holes and the surrounding conductive pattern with a dry film resist.

Thin Core

Thin laminate, usually less than 0.005 inches thick.

Through-Hole

Of a component, also spelled "thru-hole".Having pins designed to be inserted into holes and soldered to pads on a printed board. Contrast with surface mount.

Thin Core

That side of the printed circuit board on which most of the components will be mounted. The opposite side contains soldering points for components.

Trace

Segment of a route. It refers to the copper path printed on a PCB. It functions similarly to an electrical wire, connecting components on a PCB board.

U

UL

Underwriter's Laboratories, Inc., a corporation supported by some underwriters for establishing safety standards on types of equipment or components.

V

Via

A plated through hole (PTH) in a Printed Circuit Board that is used to provide electrical connection between a trace on one layer of the Printed Circuit Board to a trace on another layer. Since it is not used to mount component leads, it is generally a small hole and pad diameter.

Via in Pad

Via-in-pad (VIP) technology basically refers to the technology by which via is placed directly beneath component contact pad, especially BGA pad with finer pitch array packages. In other words, VIP technology leads to vias plated or hidden under BGA pad, requiring that PCB manufacturer should plug via with resin prior to carrying out copper plating on the via to make it invisible.

V-Cut

This is an incomplete cut through a panel, which is often used to help break apart panels of PCBs into single units.

W

Wave Soldering

A machine is used to coat the solder side of a PCB with molten solder speeding up the assembly process.